In the

anatomy Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having its ...

of humans and various other

tetrapod Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids ( reptiles, including dinosaurs and therefore birds) and synapsids (pelycosaurs, extinct theraps ...

s, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear from the middle ear. Its function is to transmit

sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the ...

from the air to the

ossicles The ossicles (also called auditory ossicles) are three bones in either middle ear that are among the smallest bones in the human body. They serve to transmit sounds from the air to the fluid-filled labyrinth (cochlea). The absence of the auditory ...

inside the middle ear, and then to the

oval window The oval window (or ''fenestra vestibuli'' or ''fenestra ovalis'') is a membrane-covered opening from the middle ear to the cochlea of the inner ear. Vibrations that contact the tympanic membrane travel through the three ossicles and into the in ...

in the fluid-filled

cochlea The cochlea is the part of the inner ear involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, in humans making 2.75 turns around its axis, the modiolus. A core component of the cochlea is the Organ of Corti, the sensory org ...

. Hence, it ultimately converts and amplifies vibration in the air to vibration in cochlear fluid. The malleus bone bridges the gap between the eardrum and the other ossicles. Rupture or

perforation of the eardrum A perforated eardrum (tympanic membrane perforation) is a hole in the eardrum. It can be caused by infection (otitis media), trauma, overpressure (loud noise), inappropriate ear clearing, and changes in middle ear pressure. An otoscope can be u ...

can lead to conductive hearing loss. Collapse or

retraction Retraction or retract(ed) may refer to: Academia * Retraction in academic publishing, withdrawals of previously published academic journal articles Mathematics * Retraction (category theory) * Retract (group theory) * Retraction (topology) Huma ...

of the eardrum can cause conductive hearing loss or cholesteatoma.

Structure

Orientation and relations

The tympanic membrane is oriented obliquely in the anteroposterior, mediolateral, and superoinferior planes. Consequently, its superoposterior end lies lateral to its anteroinferior end. Anatomically, it relates superiorly to the middle cranial fossa, posteriorly to the ossicles and facial nerve, inferiorly to the parotid gland, and anteriorly to the temporomandibular joint.

Regions

The eardrum is divided into two general regions: the

pars flaccida In human anatomy, the pars flaccida of tympanic membrane or Shrapnell's membrane (also known as Rivinus' ligament) is the small, triangular, flaccid portion of the tympanic membrane, or eardrum. It lies above the malleolar folds attached directly ...

and the

pars tensa In the anatomy Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old ...

. The relatively fragile pars flaccida lies above the lateral

process A process is a series or set of activities that interact to produce a result; it may occur once-only or be recurrent or periodic. Things called a process include: Business and management *Business process, activities that produce a specific se ...

of the malleus between the

notch of Rivinus {{Technical, date=November 2013 The Notch of Rivinus is a small defect in the posterior edge of the bony annular tympanic ring. The defect is located just superior to the tympano-mastoid suture line in the posterior ear canal The ear canal (ex ...

and the anterior and posterior malleal folds. Consisting of two layers and appearing slightly pinkish in hue, it is associated with

Eustachian tube In anatomy, the Eustachian tube, also known as the auditory tube or pharyngotympanic tube, is a tube that links the nasopharynx to the middle ear, of which it is also a part. In adult humans, the Eustachian tube is approximately long and in d ...

dysfunction and cholesteatomas. The larger pars tensa consists of three layers:

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...

, fibrous tissue, and

mucosa A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...

. Its thick periphery forms a fibrocartilaginous ring called the

annulus tympanicus Annulus (or anulus) or annular indicates a ring- or donut-shaped area or structure. It may refer to: Human anatomy * ''Anulus fibrosus disci intervertebralis'', spinal structure * Annulus of Zinn, a.k.a. annular tendon or ''anulus tendineus com ...

or Gerlach's ligament. while the central umbo tents inward at the level of the tip of malleus. The middle fibrous layer, containing radial, circular, and parabolic fibers, encloses the handle of malleus. Though comparatively robust, the pars tensa is the region more commonly associated with perforations.

Umbo

The manubrium ( la, handle) of the malleus is firmly attached to the medial surface of the membrane as far as its center, drawing it toward the

tympanic cavity The tympanic cavity is a small cavity surrounding the bones of the middle ear. Within it sit the ossicles, three small bones that transmit vibrations used in the detection of sound. Structure On its lateral surface, it abuts the external auditory ...

. The lateral surface of the membrane is thus concave. The most depressed aspect of this concavity is termed the umbo ( la,

shield boss A shield boss, or umbo, is a round, convex or conical piece of material at the centre of a shield. Shield bosses (or sometimes, just "bosses") are usually made of thick metal but could also be made of wood. The boss was originally designed to de ...

Nerve supply

Sensation of the outer surface of the tympanic membrane is supplied mainly by the auriculotemporal nerve, a branch of the

mandibular nerve In neuroanatomy, the mandibular nerve (V) is the largest of the three divisions of the trigeminal nerve, the fifth cranial nerve (CN V). Unlike the other divisions of the trigeminal nerve (ophthalmic nerve, maxillary nerve) which contain only aff ...

(

cranial nerve Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), of which there are conventionally considered twelve pairs. Cranial nerves relay information between the brain and parts of the body, primarily to and ...

V₃), with contributions from the auricular branch of the vagus nerve (

cranial nerve X The vagus nerve, also known as the tenth cranial nerve, cranial nerve X, or simply CN X, is a cranial nerve that interfaces with the parasympathetic control of the heart, lungs, and digestive tract. It comprises two nerves—the left and right v ...

), the facial nerve (cranial nerve VII), and possibly the

glossopharyngeal nerve The glossopharyngeal nerve (), also known as the ninth cranial nerve, cranial nerve IX, or simply CN IX, is a cranial nerve that exits the brainstem from the sides of the upper Medulla oblongata, medulla, just anterior (closer to the nose) to t ...

(cranial nerve IX). The inner surface of the tympanic membrane is innervated by the glossopharyngeal nerve.

Clinical significance

Examination

When the eardrum is illuminated during a

medical examination In a physical examination, medical examination, or clinical examination, a medical practitioner examines a patient for any possible medical signs or symptoms of a medical condition. It generally consists of a series of questions about the patient ...

, a cone of light radiates from the tip of the malleus to the periphery in the anteroinferior quadrant, this is what is known clinically as 5 o'clock.

Rupture

Unintentional perforation (rupture) has been described in blast injuries and air travel, typically in patients experiencing

upper respiratory The respiratory tract is the subdivision of the respiratory system involved with the process of respiration in mammals. The respiratory tract is lined with respiratory epithelium as respiratory mucosa. Air is breathed in through the nose to t ...

congestion that prevents equalization of pressure in the middle ear. It is also known to occur in swimming,

diving Diving most often refers to: * Diving (sport), the sport of jumping into deep water * Underwater diving, human activity underwater for recreational or occupational purposes Diving or Dive may also refer to: Sports * Dive (American football), a ...

(including

scuba diving Scuba diving is a mode of underwater diving whereby divers use breathing equipment that is completely independent of a surface air supply. The name "scuba", an acronym for "Self-Contained Underwater Breathing Apparatus", was coined by Chris ...

), and

martial arts Martial arts are codified systems and traditions of combat practiced for a number of reasons such as self-defense; military and law enforcement applications; combat sport, competition; physical, mental, and spiritual development; entertainment; a ...

. Patients with tympanic membrane rupture may experience bleeding, tinnitus,

hearing loss Hearing loss is a partial or total inability to Hearing, hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to Language ...

, or disequilibrium ( vertigo). However, they rarely require medical intervention, as between 80 and 95 percent of ruptures recover completely within two to four weeks. The prognosis becomes more guarded as the force of injury increases.

Surgical puncture for treatment of middle ear infections

The pressure of fluid in an infected middle ear onto the eardrum may cause it to rupture. Usually, this consists of a small hole (perforation), which allows fluid to drain out. If this does not occur naturally, a myringotomy (tympanotomy, tympanostomy) can be performed. A myringotomy is a surgical procedure in which a tiny incision is created in the eardrum to relieve pressure caused by excessive buildup of fluid, or to drain

pus Pus is an exudate, typically white-yellow, yellow, or yellow-brown, formed at the site of inflammation during bacterial or fungal infection. An accumulation of pus in an enclosed tissue space is known as an abscess, whereas a visible collection ...

from the middle ear. The fluid or pus comes from a middle ear infection (

otitis media Otitis media is a group of inflammatory diseases of the middle ear. One of the two main types is acute otitis media (AOM), an infection of rapid onset that usually presents with ear pain. In young children this may result in pulling at the ear, ...

), which is a common problem in children. A tympanostomy tube is inserted into the eardrum to keep the middle ear aerated for a prolonged time and to prevent reaccumulation of fluid. Without the insertion of a tube, the incision usually heals spontaneously in two to three weeks. Depending on the type, the tube is either naturally extruded in 6 to 12 months or removed during a minor procedure. Those requiring myringotomy usually have an obstructed or dysfunctional

eustachian tube In anatomy, the Eustachian tube, also known as the auditory tube or pharyngotympanic tube, is a tube that links the nasopharynx to the middle ear, of which it is also a part. In adult humans, the Eustachian tube is approximately long and in d ...

that is unable to perform drainage or ventilation in its usual fashion. Before the invention of antibiotics, myringotomy without tube placement was also used as a major treatment of severe acute otitis media. In some cases, the pressure of fluid in an infected middle ear is great enough to cause the eardrum to rupture naturally. Usually, this consists of a small hole (perforation), from which fluid can drain.

Society and culture

The

Bajau The Sama-Bajau include several Austronesian ethnic groups of Maritime Southeast Asia. The name collectively refers to related people who usually call themselves the Sama or Samah (formally A'a Sama, "Sama people"); or are known by the exonym ...

people of the Pacific intentionally rupture their eardrums at an early age to facilitate diving and hunting at sea. Many older Bajau therefore have difficulties hearing.

Additional images

File:Anatomy of the Human Ear en.svg, Anatomy of the human right ear. File:Gray907.png, External and middle ear, right side, opened from the front (coronal section) File:Gray908.png, Horizontal section through left ear; upper half of section File:Gray912.png, The right membrana tympani with the hammer and the chorda tympani, viewed from within, from behind, and from above File:Gray915.png, Auditory tube, laid open by a cut in its long axis File:Gray919.png, Chain of ossicles and their ligaments, seen from the front in a vertical, transverse section of the tympanum ympanic cavityFile:Gray909.png, Right eardrum as seen through a speculum File:Normal Left Tympanic Membrane.jpg, This is a normal left eardrum. File:Tympanic membrane viewed by otoscope.png, Tympanic membrane viewed by otoscope File:Traumatic Perforation of the Tympanic Membrane.jpg, The oval perforation in this left tympanic membrane was the result of a slap on the ear File:Subtotal Perforation of the right tympanic membrane.tif, A subtotal perforation of the right tympanic membrane resulting from a previous severe otitis media File:TM RIGHT NORMAL.jpg, A normal human right tympanic membrane (eardrum) File:Frog on leaf with eardrum.jpg, Frog on leaf showing eardrum

References

External links

Diagram at Georgia State University

{{Authority control Auditory system Ear